add support to override platform

Signed-off-by: Casey Lee <[email protected]>

cmd/platforms.go

@@ -0,0 +1,25 @@
+package cmd
+
+import (
+	"strings"
+)
+
+func (i *Input) newPlatforms() map[string]string {
+	platforms := map[string]string{
+		"ubuntu-latest":  "ubuntu:18.04",
+		"ubuntu-18.04":   "ubuntu:18.04",
+		"ubuntu-16.04":   "ubuntu:16.04",
+		"windows-latest": "",
+		"windows-2019":   "",
+		"macos-latest":   "",
+		"macos-10.15":    "",
+	}
+
+	for _, p := range i.platforms {
+		pParts := strings.Split(p, "=")
+		if len(pParts) == 2 {
+			platforms[pParts[0]] = pParts[1]
+		}
+	}
+	return platforms
+}